The
number of uses for nanocomposite materials is staggering. The
material has been the source of some revolutionary breakthroughs in
many areas of research. One of the most beneficial places for
nanocomposite materials has been in battery research.

Battery
research is important for many uses ranging from electronic devices
like notebooks with longer run times to electric
cars that have greater driving ranges. Two of the key components
in the structure of a battery are the anode and cathode. Researchers
have developed a new anode structure built using silicon-carbon
nanocomposite materials. The new anode promises to allow a massive
improvement in the performance of current lithium-ion
batteries.

The breakthrough
anode uses self-assembling nanocomposite material in a
technique that results in a structure with very finely tuned
properties. The new breakthrough isn’t the first time researchers
have tried to use silicon-based anodes in lithium-ion batteries.
Previous attempts to design a silicon-based anode failed because the
anodes were not stable enough for practical use.

The reason
the silicon-based anodes previously designed weren't practical for
normal use was that expansion and contraction of the anode as lithium
ions enter and leave the silicon created cracks that cause anode
failure rapidly. The new anode breakthrough using the silicon-carbon
nanocomposite material uses a "bottom-up" self-assembly
technique to tune the structure of the anode to overcome the
shortcomings of the previous silicon-based anodes.

Gleb
Yushin, an assistant professor in the School of Materials Science and
Engineering at the Georgia Institute of Technology said, "Development
of a novel approach to producing hierarchical anode or cathode
particles with controlled properties opens the door to many new
directions for lithium-ion battery technology."

The
composite anode is made starting with the formation of a highly
conductive branching structure made from carbon black material. The
researchers says that the branching structure resembles the branches
of a tree. The carbon black used in the structures is then annealed
in a high-temperature tube furnace. A chemical vapor is then
introduced to create silicon nanosphere with diameters under 30nm and
the spheres resemble apples hanging on a tree.

After the
nanospheres are formed and the chemical vapor is deposited, graphitic
carbon is used as an electrically conductive binder and the
silicon-carbon composites self-assemble into ridged spheres with open
and interconnected internal pores. The spheres created in the process
range from 10 to 30microns in size and are used to form the new
anode. The pores and internal channels allow the liquid electrolyte
used in a battery to enter the spheres rapidly along with lithium
ions for quick battery charging and the spheres can expand without
cracking resulting in no breakdown of the anode.

The
researchers say that a battery using the new anode would be
able to survive thousands of charge and discharge cycles without
degradation while providing a ten times increase in the storage
capacity of the battery. The process used for building the anodes is
also compatible with current battery construction processes.

Yushin
said, "If this technology can offer a lower cost on a capacity
basis, or lighter weight compared to current techniques, this will
help advance the market for lithium batteries," he said. "If
we are able to produce less expensive batteries that last for a long
time, this could also facilitate the adoption of many 'green'
technologies, such as electric vehicles or solar cells."